CUTTING EDGE - SENESCENT BALB C MICE EXHIBIT DECREASED EXPRESSION OF LAMBDA-5 SURROGATE LIGHT-CHAINS AND REDUCED DEVELOPMENT WITHIN THE PRE-B-CELL COMPARTMENT/

Although senescent BALB/c mice (similar to 2 years old) have reduced n umbers of small pre-B cells, early pre-B cells (CD43(+)CD25(+)B220(+)) are present in comparable numbers within the bone marrow of both youn g (3-6-month-old) and senescent BALB/c mice, The transition of CD43(+) pre-B cells to the CD43(-) pre-B cell compartments is dependent on pr oliferation and clonal maturation dictated by the pre-B cell receptor (mu/lambda 5/VpreB). In vivo, senescent CD43(+)B220(+) pro-B/early pre -B cells demonstrated reduction of lambda 5 mRNA, by RT-PCR analysis, and of both surface and cytoplasmic W protein, Decreased lambda 5 prot ein expression was also seen among pro-B/pre-B cells derived from sene scent bone marrow after stimulation in vitro with IL-7, We. propose th at diminished expression of the lambda 5 surrogate light chain results in decreased pre-B cell receptor formation and contributes to reduced recruitment of nascent CD43(+) pre-B cells into the CD43- large and s mall pre-B cell compartments.